The origin of many mental dysfunctions is not obvious. It may include a biochemical lesion, a diffuse structural lesion, or no apparent lesion at all. The absence of a recognizable lesion in a behaviorally abnormal brain presents a formidable challenge and has contributed to the considerable controversy concerning the very basis for abnormality, not to mention confusion over diagnosis and prognosis. The functional state of the brain changes from moment to moment, reflecting external sensory stimulation and intrinsic neural activity. Various degrees of brain activation are accompanied by different levels of metabolic demand. Inability to obtain an adequate nutrient supply to cover the metabolic demand during periods of higher levels of neural activity should have serious consequences to mental function. Prolonged accumulation of metabolic wastes in the brain tissue may have equally serious consequences. These are probably important reasons for early studies of cerebral blood flow in patients with mental dysfunctions by S. Kety and his colleagues. Substantial progress has been made in this area, but we still do not know the importance of the interaction between cerebral flow and its metabolism in the different functional states of the brain, normal or abnormal. Our major objective is to quantitatively establish the normal baseline concerning the relationship between local cerebral glucose utilization, regional cerebral blood flow, and function. As a model system, the entire auditory system will be studied. Auditory stimulation will be used while the functional activation of auditory structures from the brainstem to cortex will be monitored by recording auditory evoked potentials from the scalp. Regional blood flow and local cerebral glucose utilization will be measured by the iodoantipyrine method and the Deoxyglucose method, respectively. In the long run, we will test the hypothesis of deficiencies in the mechanisms concerning metabolic control of cerebral blood flow as a possible factor to certain categories of mental dysfunction and developmental disability. This shall be possible since it is becoming feasible to measure all the experimental parameters in human subjects.